I gratefully acknowledge the support of the Slovenian Research Agency, grant no. P4-133.

1. Basic histology for honeybee research
<ol>
	<li>Dissection of honeybee tissue 
	NOTE: For the dissection of worker bees, use a dissecting microscope with an LED light source. The most useful magnification is ~20x.
	<ol>
		<li>Manipulation and dissection
		<ol>
			<li>Carefully take a worker bee with forceps and put it on ice (or into the freezer at -20 &#176;C) for 2 min to immobilize it22. Pin the bee on the Petri dish diagonally through the uppermost back portion of th...

<ol>
	<li>Ruttner, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Naturgeschichte der Honigbienen. , (1992).</li><li>Jordan, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Kleine+Bienenkunde.">Kleine Bienenkunde.</a> &#214;sterreichischer Agrarverlag Wien M&#252;nchen. , 41-45 (1964).</li><li>Snodgrass, R. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+Anatomy+of+the+Honey+Bee.">The Anatomy of the Honey Bee.</a> The Hive and the Honey Bee. , 111-113 (1975).</li><li>Snodgrass, R. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> The Anatomy of the Honey Bee. , (2004).</li><li>Hrassnigg, N., Crailsheim, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Adaptation+of+hypopharyngeal+gland+development+to+the+brood+status+of+honeybee+(Apis+mellifera+L.)+colonies.">Adaptation of hypopharyngeal gland development to the brood status of honeybee (Apis mellifera L.) colonies.</a> Journal of Insect Physiology. 44 (10), 929-939 (1998).</li><li>Smodi&#353; &#352;kerl, M. I., Gregorc, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Characteristics+of+hypopharyngeal+glands+in+honeybees+(Apis+mellifera+carnica)+from+a+nurse+colony.">Characteristics of hypopharyngeal glands in honeybees (Apis mellifera carnica) from a nurse colony.</a> Slovenian Veterinary Research. 52 (2), 67-74 (2015).</li><li>Kubo, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Change+in+the+expression+of+hypopharyngeal-gland+proteins+of+the+worker+honeybees+(Apis+mellifera+L.)+with+age+and/or+role.">Change in the expression of hypopharyngeal-gland proteins of the worker honeybees (Apis mellifera L.) with age and/or role.</a> Journal of Biochemistry. 119 (2), 291-295 (1996).</li><li>Sammataro, D., Yoder, J. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Honey bee colony health: Challenges and sustainable solutions. , 302 (2012).</li><li>Crailsheim, K., Stolberg, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Influence+of+diet,+age+and+colony+condition+upon+intestinal+proteolytic+activity+and+size+of+the+hypopharyngeal+glands+in+the+honeybee+(Apis+mellifera+L.).">Influence of diet, age and colony condition upon intestinal proteolytic activity and size of the hypopharyngeal glands in the honeybee (Apis mellifera L.).</a> Journal of Insect Physiology. 35 (8), 595-602 (1998).</li><li>Smodi&#353; &#352;kerl, M. I., Gregorc, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Heat+shock+proteins+and+cell+death+in+situ+localisation+in+hypopharyngeal+glands+of+honeybee+(Apis+mellifera+carnica)+workers+after+imidacloprid+or+coumaphos+treatment.">Heat shock proteins and cell death in situ localisation in hypopharyngeal glands of honeybee (Apis mellifera carnica) workers after imidacloprid or coumaphos treatment.</a> Apidologie. 41 (1), 73-86 (2010).</li><li>Gregorc, A., Bowen, I. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+histochemical+characterisation+of+cell+death+in+honeybee+larvae+midgut+after+treatment+with+Paenibacillus+larvae,+Amitraz+and+Oxytetracycline.">The histochemical characterisation of cell death in honeybee larvae midgut after treatment with Paenibacillus larvae, Amitraz and Oxytetracycline.</a> Cell Biology International. 24 (5), 319-324 (2000).</li><li>Higes, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Apoptosis+in+the+pathogenesis+of+Nosema+ceranae+(Microsporidia:+Nosematidae)+in+honey+bees+(Apis+mellifera).">Apoptosis in the pathogenesis of Nosema ceranae (Microsporidia: Nosematidae) in honey bees (Apis mellifera).</a> Environmental Microbiology Reports. 5 (4), 530-536 (2013).</li><li>Kurze, C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Infection+dynamics+of+Nosema+ceranae+in+honey+bee+midgut+and+host+cell+apoptosis.">Infection dynamics of Nosema ceranae in honey bee midgut and host cell apoptosis.</a> Journal of Invertebrate Pathology. 154, 1-4 (2018).</li><li>Johnson, R. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Honey+bee+toxicology.">Honey bee toxicology.</a> Annual Review of Entomology. 60 (1), 415-434 (2005).</li><li>Gashout, H. A., Guzman-Novoa, E., Goodwin, P. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Synthetic+and+natural+acaricides+impair+hygienic+and+foraging+behaviors+of+honey+bees.">Synthetic and natural acaricides impair hygienic and foraging behaviors of honey bees.</a> Apidologie. 51 (6), 1155-1165 (2020).</li><li>McMenamin, A. J., Genersch, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Honey+bee+colony+losses+and+associated+viruses.">Honey bee colony losses and associated viruses.</a> Current Opinion in Insect Science. 8, 121-129 (2015).</li><li>Ramsey, S. D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Varroa+destructor+feeds+primarily+on+honey+bee+fat+body+tissue+and+not+hemolymph.">Varroa destructor feeds primarily on honey bee fat body tissue and not hemolymph.</a> Proceedings of the National Academy of Sciences USA. 116 (5), 1792-1801 (2019).</li><li>Requier, F., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Honey+bee+diet+in+intensive+farmland+habitats+reveals+an+unexpectedly+high+flower+richness+and+a+major+role+of+weeds.">Honey bee diet in intensive farmland habitats reveals an unexpectedly high flower richness and a major role of weeds.</a> Ecological Applications. 25 (4), 881-890 (2015).</li><li>Santos, C., Serr&#227;o, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Histology+of+the+ileum+in+bees+(Hymenoptera,+Apoidea).">Histology of the ileum in bees (Hymenoptera, Apoidea).</a> Brazilian Journal of Morphological Sciences. 23 (3), 405-413 (2006).</li><li>Suwannapong, G., Saichon, C., Benbow, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Histochemical+comparison+of+the+hypopharyngeal+gland+in+Apis+cerana+Fabricius,+1793+workers+and+Apis+mellifera+Linnaeus,+1758+workers.">Histochemical comparison of the hypopharyngeal gland in Apis cerana Fabricius, 1793 workers and Apis mellifera Linnaeus, 1758 workers.</a> Psyche: A Journal of Entomology. , (2010).</li><li>Ceylan, A., Sevin, S., &#214;zgen&#231;, &. #. 2. 1. 4. ;. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Histomorphological+and+histochemical+structure+of+the+midgut+and+hindgut+of+the+Caucasian+honey+bee+(Apis+mellifera+caucasia).">Histomorphological and histochemical structure of the midgut and hindgut of the Caucasian honey bee (Apis mellifera caucasia).</a> Turkish Journal of Veterinary and Animal Sciences. 43 (6), 747-753 (2019).</li><li>Human, H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Miscellaneous+standard+methods+for+Apis+mellifera+research.">Miscellaneous standard methods for Apis mellifera research.</a> Journal of Apicultural Research. 52 (4), 1-53 (2013).</li><li>Gregorc, A., Smodi&#353; &#352;kerl, M. I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Toxicological+and+immunohistochemical+testing+of+honeybees+after+oxalic+and+rotenone+treatments.">Toxicological and immunohistochemical testing of honeybees after oxalic and rotenone treatments.</a> Apidologie. 38 (3), 296-305 (2007).</li><li>Carreck, N. L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Standard+methods+for+Apis+mellifera+anatomy+and+dissection.">Standard methods for Apis mellifera anatomy and dissection.</a> Journal of Apicultural Research. 52 (4), 1-40 (2013).</li><li>Bowen, I. D., Bowen, S. M., Jones, A. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Mitosis and apoptosis: Matters of Life and Death. , (1998).</li><li>Eisenberg-Lerner, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Life+and+death+partners:+apoptosis,+autophagy+and+the+cross-talk+between+them.">Life and death partners: apoptosis, autophagy and the cross-talk between them.</a> Cell Death and Differentiation. 16 (7), 966-975 (2009).</li><li>Bowen, I. D., Mullarkey, K., Morgan, S. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Programmed+cell+death+in+the+salivary+gland+of+the+blow+fly+Calliphora+vomitoria.">Programmed cell death in the salivary gland of the blow fly Calliphora vomitoria.</a> Microscopy Research Techniques. 34, 202-207 (1996).</li><li>D'Arcy, M. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cell+death:+a+review+of+the+major+forms+of+apoptosis,+necrosis+and+autophagy.">Cell death: a review of the major forms of apoptosis, necrosis and autophagy.</a> Cell Biology International. 43 (6), 582-592 (2019).</li><li>Matylevitch, N. P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Apoptosis+and+accidental+cell+death+in+cultured+human+keratinocytes+after+thermal+injury.">Apoptosis and accidental cell death in cultured human keratinocytes after thermal injury.</a> American Journal of Pathology. 153 (2), 567-577 (1998).</li><li>Perry, S. W., Epstein, L. G., Gelbard, H. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Simultaneous+in+situ+detection+of+apoptosis+and+necrosis+in+monolayer+cultures+by+TUNEL+and+trypan+blue+staining.">Simultaneous in situ detection of apoptosis and necrosis in monolayer cultures by TUNEL and trypan blue staining.</a> BioTechniques. 22 (6), 1102-1106 (1997).</li><li>Cuello-Carrion, F. D., Ciocca, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Improved+detection+of+apoptotic+cells+using+a+modified+in+situ+TUNEL+technique.">Improved detection of apoptotic cells using a modified in situ TUNEL technique.</a> Journal of Histochemistry and Cytochemistry. 47 (6), 837-839 (1999).</li><li>Gregorc, A., Bowen, I. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Programmed+cell+death+in+the+honeybee+(Apis+mellifera+L.)+larvae+midgut.">Programmed cell death in the honeybee (Apis mellifera L.) larvae midgut.</a> Cell Biology International. 21 (3), 151-158 (1997).</li><li>Gregorc, A., Poga&#269;nik, A., Bowen, I. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cell+death+in+honey+bee+(Apis+mellifera)+larvae+treated+with+oxalic+or+formic+acid.">Cell death in honey bee (Apis mellifera) larvae treated with oxalic or formic acid.</a> Apidologie. 35 (5), 453-460 (2004).</li></ol>

The author has no conflicts of interest.

In living organisms, cell death is defined as apoptosis or necrosis25&#160;and can be accompanied by autophagy26. The difference between apoptotic and necrotic cells is that apoptosis is a form of programmed cell death and appears in normal cells, whereas necrosis occurs due to lethal conditions (e.g., accident, disease)27,28. Apoptosis can be detected using assay kits based on the TUNEL technique (detection ofDNA f...

Honeybees (Apis mellifera L.) are, among other wild pollinators, the most important pollinators of agricultural plants. Over thousands of years, the changing environment has influenced bees to adapt their morphology, physiology, behavior, and tolerance to several pathogens and parasites. Therefore, honeybees have developed a highly diverse range of species and subspecies around the globe1. These results are consistent with previous findings, that there is genetic variation in the honeybee&#39;s digestive tract structure, but also suggest that alterations of the midgut are due to environmental factors2,3.
The digestive tract of the honeybee has three main parts: foregut, midgut (ventriculus), and hindgut4. The ventriculus is an essential organ for the digestion of pollen and nectar/honey; in the hindgut, osmotic control takes place through absorption of water and ions2. The hypopharyngeal glands (HPGs) of honeybee workers are located in the head and synthesize and secrete royal jelly components to feed the brood, the queen, and members of the colony. Their size changes with age and tasks and depends on proper nutrition (quality pollen). Nurse workers aged 6 to 18 days perform brood rearing, and the size of HPGs increases5,6. In forager bees, the HPGs degenerate and only secrete enzymes that are important to convert the complex sugars into simple ones (&#945;-glucosidases, leucine arylamidase, invertase) in honey7.
Honeybees are exposed to several biotic and abiotic stressors8, and the digestive tract can be affected by several negative stimulants. The first barrier that protects the organism from pathogens is the peritrophic membrane in the midgut, which consists of intestinal mucosa to protect against pathogens4. The development and function of HPGs depend on diet, age, and colony condition9, and are affected by insecticides, acaricides10, and pathogens11,12,13. Acaricide residues in the hive due to varroa control treatment and pesticides from the environment affect forager bees and nurse bees14,15. The greatest threat to honeybee colonies is the mite Varroa destructor, both as a vector of viruses contributing to colony losses16&#160;and as a consumer of the host&#39;s fat body (an important vital organ in honeybees), which consequently affects the individual&#39;s body and colony functions17.
However, intensive farmland habitats can provide a short-term food supply for honeybees. Therefore, agri-environmental schemes should enhance the availability of honey flowers in agricultural landscapes18. To assess the morphology of different subspecies6,19,20,21&#160;or sublethal effects of these factors at the cell or tissue levels, especially midgut and HPGs, histological and immunohistochemical methods are practical and sufficiently accurate to be used in histology research in honeybees.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>2-Propanol</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>ApopTag Peroxidase kit (ApopTag Peroxidase In Situ Apoptosis Detection)</td>
			<td>Sigma-Aldrich</td>
			<td>S7100</td>
			<td>Assay B, https://www.sigmaaldrich.com/SI/en/product/mm/s7100?gclid=CjwKCA 
			jw7vuUBhBUEiwAEdu2pPanI9SE 
			j81ZTl-nLHEoxXAv7ViKwPA_QRx 
			H7fciMRNcYwR7lbPQbhoCqcQQA 
			vD_BwE; Positive controls included in S7101</td>
		</tr>
		<tr>
			<td>Covers</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>DeadEnd Colorimetric TUNEL system</td>
			<td>Promega</td>
			<td>G7360</td>
			<td>Assay A, https://worldwide.promega.com/products/cell-health-assays/apoptosis-assays/deadend-colorimetric-tunel-system/?catNum=G7360</td>
		</tr>
		<tr>
			<td>Dissecting microscope&#160; (for bee dissection)</td>
			<td>Zeiss</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Distilled water</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Embedding cassette</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>EnVision System alkaline phosphatase kit</td>
			<td>Dako</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Eosin Y Solution</td>
			<td>Sigma-Aldrich</td>
			<td></td>
			<td>alcoholic</td>
		</tr>
		<tr>
			<td>Ethanol</td>
			<td></td>
			<td></td>
			<td>95% (or less pure), 90%, 80%</td>
		</tr>
		<tr>
			<td>Faramount mounting medium, aqueous</td>
			<td>Dako</td>
			<td></td>
			<td>mounting medium</td>
		</tr>
		<tr>
			<td>Flattening table</td>
			<td>Leica</td>
			<td>HI1220</td>
			<td></td>
		</tr>
		<tr>
			<td>Forceps&#160; (for bee dissection)</td>
			<td>Fine science tools</td>
			<td>11294-00</td>
			<td>Standard #4</td>
		</tr>
		<tr>
			<td>Formalin 10%</td>
			<td></td>
			<td></td>
			<td>Formaldehyde</td>
		</tr>
		<tr>
			<td>Hematoxylin</td>
			<td>Sigma-Aldrich</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>HistoChoice Clearing Agent</td>
			<td>Sigma-Aldrich</td>
			<td></td>
			<td>clearing agent</td>
		</tr>
		<tr>
			<td>Hydrogen peroxidase 3%</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Incubator</td>
			<td>BioRad</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Insect pins&#160; (for bee dissection)</td>
			<td>Entosphinx</td>
			<td>44594</td>
			<td>Insect pins stainless steel &#8211; white, size 2</td>
		</tr>
		<tr>
			<td>ISCDDK, AP (In Situ Cell Death Detecteion Kit, Alkaline Phosphatase)</td>
			<td>Roche</td>
			<td>11684809910</td>
			<td>Assay C, https://www.sigmaaldrich.com/deepweb/assets/sigmaaldrich/product/documents/362/737/11684809910b 
			ul.pdf</td>
		</tr>
		<tr>
			<td>KH2PO4</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Lab clock</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Light microscope</td>
			<td>Leica</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Microscope slides</td>
			<td></td>
			<td></td>
			<td>Box with the slides must be preserved in a plastic wrap to prevent dust</td>
		</tr>
		<tr>
			<td>Microtome</td>
			<td>Leica</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Modular tissue embedding station</td>
			<td>Leica</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Na2HPO4</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>NaCl</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Paraformaldehyde 4%</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Paraplast</td>
			<td>Leica</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Pasteur pipettes</td>
			<td></td>
			<td></td>
			<td>1.5 mL; 3 mL</td>
		</tr>
		<tr>
			<td>PBS</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Petri dish&#160; (for bee dissection)</td>
			<td></td>
			<td></td>
			<td>Filled with condensation silicon&#160; (Xantoprene L blue and Universal liquid plus activator)</td>
		</tr>
		<tr>
			<td>Proteinase K</td>
			<td>Merck</td>
			<td>21627</td>
			<td></td>
		</tr>
		<tr>
			<td>Ringers&#39; solution&#160; (for bee dissection)</td>
			<td></td>
			<td></td>
			<td>7.5 g NaCL, 2.38 g Na2HPO4, 2.72 g KH2PO4, 1 L distilled water</td>
		</tr>
		<tr>
			<td>Scissors&#160; (for bee dissection)</td>
			<td>Fine science tools</td>
			<td>1406-09, 14061-09</td>
			<td>Straight and curved, 9 cm</td>
		</tr>
		<tr>
			<td>Universal liquid plus activator&#160; (for bee dissection)</td>
			<td>Kulzer</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Watchmaker&#8217;s forceps (for bee dissection)</td>
			<td>Fine science tools</td>
			<td>91100-12</td>
			<td></td>
		</tr>
		<tr>
			<td>Water bath</td>
			<td>Leica</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Watercolor brush</td>
			<td></td>
			<td></td>
			<td>2x</td>
		</tr>
		<tr>
			<td>Xantoprene L blue&#160; (for bee dissection)</td>
			<td>Kulzer</td>
			<td></td>
			<td></td>
		</tr>
	</tbody>
</table>

histology basics and cell death detection in honeybee tissue

Honeybees (Apis mellifera L.) inside the hive (nurse workers and other hive bees) and outside the hive (foragers) are exposed to climate and weather changes, various pesticides, pathogens, and malnutrition, mainly entering through the mouth and primarily affecting the digestive tracts of adult bees. To understand and prevent the effects of such external and internal stressors on honeybees, one useful research method is the immunohistochemical method. A basic protocol is described to prepare the midgut (ventriculus) and hypopharyngeal glands (HPGs) of adult bees for histological analysis. A detailed methodology is described to assess the level of cell damage and distinguish necrosis from programmed cell death (apoptosis) as a natural process of tissue regeneration. The results of adult honeybee treatment with oxalic acid and pesticides (insecticide and acaricide) and the determination of cell death in the ventriculus and HPGs are presented. The pros and cons of the methodology are also discussed.

Cell death detection in the midgut 
Newly emerged worker bees (Apis mellifera carnica) from the experimental apiary at the Agricultural Institute of Slovenia in Ljubljana were individually treated with 3% oxalic acid (OA)23. OA is frequently used in beekeeping for Varroa destructor control. After the treatment, the worker bees (three from each group) were immobilized on ice. The midgut was dissected and fixed it in 10% formalin. The tissue was then dehydrate...

Watch this Scientific Journal Video about Histology Basics and Cell Death Detection in Honeybee Tissue at JoVE.com

Histology Basics and Cell Death Detection in Honeybee Tissue

Immunohistochemical methods are useful in honeybee research to detect and assess the level of apoptosis and necrosis in the midgut and hypopharyngeal glands of adult bees.

Honeybees (Apis mellifera L.) inside the hive (nurse workers and other hive bees) and outside the hive (foragers) are exposed to climate and weather ...

This protocol is useful in many biological and toxicological studies of honeybees treated with pesticides. It helps to detect the cellular responses of honeybee tissue of acaricides that are used in bee colonies for the treatment against Varroa mites. It is a powerful tool for the detection of sub-little effects on tissue in combination with behavior of bees or other beneficial insects.To begin, carefully take a worker bee with forceps and put it on ice or freezer at minus 20 degrees Celsius for two minutes to immobilize it. Pin the bee on the Petri dish diagonally through the uppermost back portion of the thorax twice from left to right and from right to left. Poor insect saline to cover the body.Place the Petri dish under the stereomicroscope, focus, and adjust. To dissect the midgut, start with the abdomen by inserting one point of the scissors under the tergite A5 in the center of the right side of the bee body. Cut to the tergite A2.Keep the inner blade of the scissors parallel with the side of the body to avoid damaging the internal organs.Turn the scissors left and cut. Gently open the left part of the abdomen and pin it. Using forceps with one hand, gently pull the honeybee stomach upward, and with scissors in the other hand, cut at the very end of the esophagus.Pull the stomach and midgut away from the abdomen and cut at the rectum. Use a pipette with insect saline solution and remove any feces or parts of the tissue. For dissection of hypopharyngeal glands, immobilize a worker bee on ice as described before.Cut the head off and place it on a smaller plate with the antenna facing up. Secure the head with two pins, one through the left compound eye and the second through the right compound eye. Make a cut across the first compound eye on the inner side of the pins, continue to the labrum, and then make another cut on the other side across the second compound eye.Cut off the antennae. Lift off the mask and cut where still attached. Take the forceps and carefully remove the glands together with the brain and part of the compound eyes.For hematoxylin and eosin staining, put the dewaxed, rehydrated sections in hematoxylin for five minutes. Then, carefully place them under running tap water for two minutes. Then, put them into distilled water for one minute and eosin for four minutes.Place the slides 96%ethanol for one minute then 2-propanol for two minutes, and finally into the clearing agent for two minutes. Add mounting medium and a cover glass and let them dry. Observe under a light microscope.Prepare Coplin jars. Prepare proteinase-K. After dewaxing and rehydrating the sections, place the slides in PBS for five minutes.Place the slides flat in the container and add proteinase-K. Wash the slides in distilled water. Quench in endogenous peroxidase at room temperature.Rinse the slides with PBS or water. Place the slides flat in the container and apply equilibration buffer for 10 seconds at room temperature. After wiping around the tissue, add the terminal deoxynucleotidyl transferase enzyme to each section, and incubate in a humidified chamber for one hour at 37 degrees Celsius.Before incubation, put moistened paper towels inside the tray around the slides and cover them with plastic wrap. After incubation, put the specimens on the rack and leave them in stop-wash buffer. After washing the slides in PBS and wiping around the tissues, add two drops of warm anti-digoxigenin peroxidase conjugate to the sections and incubate for 30 minutes in a humidified container.After washing in PBS, prepare working strength-peroxidase substrate, cover the sections with peroxidase substrate, and stain for five minutes. Place the slide under the microscope and determine the optimal staining time. After washing the slides in a staining rack and distilled water, incubate the slides in distilled water for five minutes.Counter-stain using hematoxylin for two minutes. Wash the slides by placing them under running tap water for three minutes and then in distilled water. Mount the slides under glass cover slips and mounting medium and leave flat to dry.Observe under a light microscope. The percentage of affected cells was calculated using a light microscope. The results indicated that the treatment with oxalic acid significantly affected the cells in the midgut.Immunostaining showed positive red or brown reaction products in the apoptotic nuclei of hypopharyngeal glands. Positive reaction product after imidacloprid or coumaphos treatment was determined in the majority of glandular cells. When lifting of the mask of the bee head, take care not to damage or pull off the parts of the hypopharyngeal glands.This technique detects subclinical changes in bees and is also suitable for the detection of other environmental effects on bees and some other living organisms.

histology-basics-and-cell-death-detection-in-honeybee-tissue

Research

JoVE Journal

Biology

1.9K Views.  Agricultural Institute of Slovenia. This protocol is useful in many biological and toxicological studies of honeybees treated with pesticides. It helps to detect the cellular responses of honeybee tissue of acaricides that are used in bee colonies for the treatment against Varroa mites. It is a powerful tool for the detection of sub-little effects on tissue in combination with behavior of bees or other beneficial insects.To begin, carefully take a worker bee with forceps and put it on ice or freezer at minus 20 degrees C...